a. Field of the Invention
The invention relates to the field of life rafts, especially those of the inflatable type. In a more particular sense the invention relates to those rafts in this general category that are provided with ballast means in the form of water-retaining chambers.
b. Statement of the Prior Art
Water-ballast chambers for rafts of the type described are, in general, old. Heretofore they have been in the form of bags or pockets spaced about the underside of the raft as shown, for example, in U.S. Pat. No. 3,092,854, issued to Manhart on June 11, 1963. Or they have comprised large, centrally disposed enclosures occupying substantially the entire or at least the major portion of the underside of the raft with side walls converging downwardly to be joined to or merge into a bottom wall, as seen for example in U.S. Pat. No. 3,883,913 issued May 20, 1975 to Givens; U.S. Pat. No. 4,001,905 issued Jan. 11, 1977, also to Givens; or U.S. Pat. No. 3,736,607 issued to Radnofsky et al.
Rafts constructed according to the teachings of the Givens and Radnofsky patents have clearly improved stability, but have the disadvantage that they are heavy, cumbersome, difficult to stow, and too expensive. Most importantly, however, they proceed on a theory of improving stability through the provision of a water ballast chamber in the form of a large, depending bag extending across the entire underside of the raft, and indeed having its deepest point directly under the floor. As indicated, such an arrangement may under most circumstances provide improved stability. However, in heavy seas, surf, or high winds, a raft of this design is thought to be highly susceptible to forces that batter the raft both above and below the water surface, as a result of which the raft is likely to be flipped over upon the occupants. In such an event, there is a very real danger of the occupants being crushed. This danger arises because as the raft flips over, the entire contents of the bag crash with great force against the floor of the raft. The contents may comprise thousands of pounds of water. This weight is likely to crush the occupants beneath the floor of the overturned raft. The desirability clearly appears, accordingly, for a raft in which no ballast is carried in the center area, and in which, should the raft overturn, the weight of the water in the ballast chamber will be directed primarily against the inflated flotation element. In these circumstances, no impact is directed against the floor, and the flotation element itself is interposed as a shock absorbent means against which the force of the ballast is directed.